1. Field of the Invention
The present invention relates to an off-line teaching apparatus which is used when a robot model displayed on a monitor is operated by using a keyboard and/or a pointing device (for example, a mouse) and which makes it possible to optimally express the action in conformity with a display form of the robot model.
2. Description of the Related Art
Recently, in order to apply a robot to a variety of workings, in general, a variety of tools are attached to a face-plate of a robot arm to allow the robot to perform the workings.
The programming for the robot includes the on-line programming (on-line teaching) and the off-line programming (off-line teaching). In the case of the on-line teaching, the arm of the robot is moved to pass through necessary points or along a locus by using a push button, an operation button, an operation handle, and a joystick so that the control unit is allowed to store the points or the locus.
When the robot is operated at the driving stage, the robot reproduces and executes the stored movement.
In the off-line teaching, the operation procedure is programmed without directly using the robot. In the case of the off-line teaching, the software is programmed such that the movement of each joint is calculated in order to move the end effector to a necessary position in a necessary direction.
The movement of the robot can be displayed in animation on a graphic terminal connected to a computer, by adding a graphic function to the system which is used to execute the off-line teaching. The off-line teaching based on the use of the graphic has the following advantages.
(1) When the operation program is debugged by using the graphic, it is possible to reduce the time and the labor as compared with a case in which an actual robot is used.
(2) It is possible for the user to begin programming before the robot is introduced. Further, various types of robots can be tested on the monitor screen to select a type of machine which is most suitable for the plan.
(3) It is possible to avoid confliction in view of surrounding situations when the movement of the robot is simulated.
(4) It is possible to use a common database of CAD/CAM. For example, when a computer for CAD/CAM stores a body shape of an automobile, the designer can designate the place to be subjected to spot welding.
In the off-line teaching system having the graphic function, a robot model is displayed on a monitor screen, and the robot model is allowed to act in accordance with an operation command given by the operator.
In such a system, it takes a long time to process the program which is executed to display the robot model in animation. Therefore, the operation command, which is inputted by the operator one after another, cannot be processed in real time. It is assumed, for example, that a pointing device such as a mouse is operated in order to move the robot model. When the load is small, then the system usually makes a sensitive response to the movement of the pointing device, and the robot model on the screen is also moved in accordance with the amount of operation of the pointing device. However, when the robot model has a complicated structure, and it is constructed by a variety of drawing lines, then the capacity of display data is large. Therefore, it is impossible to make the sensitive response to the movement of the pointing device, and a considerably delay occurs in the response.
In such a case, the operator misunderstands that the operation command is not inputted into the system. As a result, the operator inputs the same operation command a number of times. Therefore, an inconvenience arises in that it is necessary to wait for the processing performed by the system to that extend (in a degree corresponding to the vain input).
In the conventional technique, the amount of action of the robot model, which is given in response to the amount of operation of the pointing device, is constant for the case in which the robot model is displayed with magnification and for the case in which the robot model is displayed with reduction. The display with magnification is made in accordance with a request that the robot model is allowed to make fine movement. However, actually, the robot model moves in a certain constant amount of action, in the same manner as in the display with reduction. Therefore, it is impossible to allow the robot model to perform, for example, an accurate and fine adjusting action.
On the other hand, for example, a robot having three axes is assumed, in which, for example, only the first axis (X axis direction) is subjected to movement by using a pointing device such as a mouse. When the pointing device is operated by the human hand, the arm is moved rightward and leftward about a supporting point of the elbow. Therefore, the pointing device is moved along a line depicted as a circular arc. In such a situation, the second axis in the Y axis direction is also subjected to movement in addition to the first axis, and it is impossible to allow the robot model to perform the desired operation (operation to make movement only for the first axis). It is feared, for example, that such a situation may obstruct the work to confirm the off-line teaching performed for the robot model.